Acceleration control for fuel injector



Nov. 10, 1959 N. F.. PRI BBLE ACCELERATION CONTROL FOR FUEL INJECTOR 3 Sheets-Sheet 1 Filed Sept. '7, 1956 muijaid v. SM

NOBLE F. PRIBBLE INVENTOR Z ATTORNEY N. F. PRIBBLE 2,911,966

ACCELERATIONCONTROL FOR FUEL INJECTOR 5 Sheets-Sheet 2 Nov. 10, 1959 Filed Sept. 7, 1956 FIGZ NOBLE F. PRIBBLE INVENTOR WWW ' ATTORNEYS Nov. 10, 1959 N. F. PRIBBLE 2,

ACCELERATION CONTROL FOR FUEL INJECTOR Filed Sept. v, 1956 3 Sheets-Sheet a FIG. 3

NOBLE E PRIBBLE INVENTOR Ta W Maw ATTORNEYS Patented Nov. 10, 1959 Thee 2,911,966 ACCELERATION CONTROL non FUEL INJECTOR Noble Franklin Pribble, Baltimore, Md., assignor to Bendix Aviation Corporation, Towson, Md., a corporation of Delaware Application September 7, 1956, Serial No. 608,525

3 Claims. (Cl. 123-119) This invention relates to a system for supplying fuel in measured amounts to the individual cylinders of an internal combustion engine in timed relation to engine operation. It relates more specifically to a system conforming to the principles of operation followed by the system disclosed in U.S. patent application Serial No. 567,688, filed February 24, 1956, in the names of Robert W. Sutton et al., for Fuel Injection System. In that system a magnetically actuated valve for each cylinder is opened for the duration of a pulse of current the time of occurrence of which is synchronized with engine rotation. The amount of fuel injected is regulated by the duration of the pulse, the pressure on the fuel being constant.

When it is desired to produce a sudden increase in the output of a throttled-air engine, it is necessary, with any type of fuel feeding, to provide a momentary increase in the amount of fuel fed, in excess of the amount necessary to sustain the rotation of the engine at the new higher output desired. This surge should be automatically developed by actuation of the throttle and its magnitude should be a function of the rate of opening of the air throttle.

It is an object of this invention to provide, in a system of the type referred to above, a means operable in response to actuation of the throttle to a position calling for an increase in the engine output, to momentarily increase the amount of fuel supplied to the engine to a value greater than that required to sustain constant engine rotation at a new higher output conforming to the new position of the throttle.

It is a further object to provide such a means which is simple and inexpensive.

These and other objects and advantages of the invention are realized in a system in which a multivibrator determines the duration of the said pulse of current actuating each fuel injection valve, the multivibrator being triggered by impulses synchronized with engine rotation, there being provided for varying the bias of said multivibrator a potentiometer actuated by the throttle and having its output applied to said multivibrator by way of a resistive voltage divider in which each resistor is shunted by a capacitor. The shunting capacitors act as a capacitive voltage divider in response to rapid movement of the accelerator, momentarily increasing the duration of the multivibrator output pulses beyond that which would be required to sustain engine speed at the new position of rest of the throttle.

In the drawings:

Fig. 1 is a schematic circuit diagram of a fuel feeding system embodying the invention.

Fig. 2 is a view in elevation of a fragment of the fuel injection system; and

Fig. 3 is a cross-sectional view in elevation of one of the fuel injection valves of the system.

' Referring more particularly to the drawing, there is shown a shaft 1, which may be the usual distributor shaft, having secured thereon for rotation therewith a cam 2. The cam is shown as six-lobed to conform to a six cylinder engine. contact of a single pole, single throw switch 3.

One contact of the switch 3 is connected, in a manner to be described later, to the control grid of one tube of a multivibrator 4, and the other contact is connected to the potential reference plane designated by the grounding symbol. The output of the multivibrator is coupled to an amplifier 5, which has its output applied by way of a conductor 6 to a wiping contact element 7 carried by, and insulated from, an arm 8 secured on the shaft 1 for rotation therewith.

The contact 7 makes sequential wiping contact with six contact segments 9, of which only two have been shown. Each of the segments 9 is connected through a respective solenoid 10 to ground. -Each solenoid actuates a valve rod 11 which is received in a seat 12 connecting with a portion of the manifold 13 adjacent a respective cylinder of the engine.

The multivibrator 4 is composed of a pair of triodes 15 and 16 having their plates connected respectively through resistors 17 and 18 to the positive terminal 19 of a source of regulated supply voltage. This terminal is also connected by way of a conductor 20 and a resistor 21 to the first mentioned contact of switch 3. The cathodes of tubes 15 and 16 are connected together and by a resistor 25 to ground. They are also connected to the grid of tube 16 by a resistor 26. This grid is also connected to the plate of tube 15 by way of a capacitor 27 and to the first mentioned contact of switch 3 by way of a capacitor 28, a diode 29, and a capacitor 30.

The conductor 20 is connected to ground by way of a pair of resistors 31 and 32. The junction of these re sistors is connected to the grid of tube 16 through a diode 33, the cathode of the diode being connected to the junction of the resistors.

A connect-ion to ground is also prvided from the conductor 20 through serially connected resistors 36, 37 and 38. A movable tap 35 on resistor 37 is mechanically driven by the throttle actuating lever or accelerator 39 or by the throttle. The movable tap 35 is connected by way of a resistor 40 and a diode 41 to the control grid of tube 15. The resistor 40 is shunted by a capacitor 42. The junction of diode 41 and the grid of tube 15 is connected to ground through a resistor 43 shunted by a capacitor 44.

The tap 35 is connected to ground by way of a capacitor 45. The junction of resistors 37 and 38 is connected to the junction of capacitor 45 and tap 35 through a resistor 46 and to a movable tap 47 on that resistor. The tap 47 is driven by a piston 48 in response to manifold pressure.

The junction of capacitor 30 and diode 29 is connected to ground through a resistor 49. The other terminal of diode 29 is connected by a diode 50 to ground.

Fig. 2 shows a pair of fuel injection valves 53 mounted on a portion of the intake manifold 13 of the engine. There is also shown a fuel pump 56 supplying fuel under pressure to the valves by way of a fuel line 57, having branches 58 individual to the valves. Manifold pressure is supplied to the piston in a cylinder 48 by way of a pipe 55. The piston is connected by means of a mechanical linkage 59 to the variable resistor 46. The manifold also houses a throttle 54 mechanically connected to the accelerator pedal 39 by a linkage 60 and to the variable resistor 37 by way of a mechanical linkage 61.

The details of one of the valves 53 are shown in the Fig. 3. As shown there, the valve rod 11 is located centrally of the valve and normally spring pressed The cam 2 drives the movable downwardly against a seat 12. 11 is a solenoid 10.

In the operation of the system described above, the cam 2 closes the switch 3 once while the contact element 7 is sweeping each of the segments 9. The first mentioned contact of the switch is alternated by this action between ground potential and the positive potential at the adjacent terminal of the resistor 21 to provide an output of square waveform as indicated at 51. This waveform is differentiated by the capacitor 30 and the resistor 49, and the negative-going excursions thereof are applied by way of the capacitor 28, to the control grid of the tube 16, providing a waveform as at 52.

The tube 16 is normally conducting and is triggered by each negative excursion into a period of non-conduction. The tube 15, which has been cut-off while tube 16 was conducting, is, by virtue of the cathode coupling, now rendered conductive and continues to conduct for a period of time, the duration of which depends upon the bias existing in its input circuit. During this period of conduction a negative-going output pulse is applied from the plate of tube 15 to the amplifier 5, and after amplification is applied to the contact element 7 and thence through the segment 9 in contact therewith to one of the solenoids 10. There it produces a current impulse of the same duration which holds open the associated valve 11, allowing fuel under pressure to spray into the manifold.

The bias applied to the control grid of the tube 15 depends in part on the voltage appearing at the movable tap 35 and in part on the proportion of that voltage level which is applied to thecontrol grid.

The voltage at the movable tap 35 is determined by the values of resistors 36, 37, 38 and 46 and the positions of the movable taps 35 and 47. The voltage at the tap 35 is increased by depression of the throttle actuating pedal or accelerator 39.

The proportion of the voltage level at the tap 35 which is applied to the control grid of tube 15 is normally determined by the voltage divider composed of resistors 40 and 43. But the capacitances of capacitors 42 and 44 are selected, in accordance with the invention, to be such that these capacitors, acting as a capacitive voltage divider, will, in response to a sudden depression of pedal 39, raise the level of the voltage at the grid of tube 15 above that which would be provided by the action of the resistive voltage divider 40, 43. When the pedal is brought to rest the capacitors will discharge through the respective resistors which they shunt and the voltage level will be determined again by the resistive voltage divider.

Since the mode of operation of the multivibrator 4 is dependent upon the values of the components in its circuitry, typical values for these elements have been applied to the drawing for consideration in connection with the following description of the operation of the circuit.

In its quiescent state the tube 16 is conducting to saturation and tube 15 cut off. The voltage dividing action of resistors 31 and 32 will provide at the grid of tube 16 a voltage of about 48 volts, with a supply potential of 150 volts. The grid is clamped at this upper level by the diode 33, and the cathodes are about 21 volt higher in potential. The conduction of the tube holds the cathodes of both tubes well above the cutoff potential of tube 15 for all values of bias applied to its grid as determined by the positions of taps 35 and 47.

The application of one of the negative-going spikes of waveform 52 to the grid of tube 16 drives the tube momentarily below saturation and the voltage on its cathode and that of tube 15 rapidly declines. This initiates conduction of tube 15. The condenser 27 is charged by the plate current of tube 15, driving the grid of tube 16 more negative and this regenerative condition continues until tube '16 is cut off and tube 15 is conducting at a level determined by the bias on tube 15. This action determines the potential difference across the resistor 26, diode Surrounding the rod 33 having been cut off by the reversed potential across it.

The capacitor 27 now begins to discharge across the resistor 26 and this continues until the voltage at the grid of tube 16 rises to a level such that conduction begins again in tube 16. This raises the voltage on the cathodes and reduces conduction in tube 15. The reduced plate current of tube 15 further reduces the charge on capacitor 27 and this regenerative action persists until tube 16 is again conducting to saturation and tube 15 is cut off. The duration of the pulse is increased by an increase of the positive bias on the grid of tube 15, since this increases the change of potential at the anode of tube 15 and shortens the grid base of tube 16 by reducing its anode-to-cathode potential at the first transition. Both of these changes require a greater change in charge of capacitor 27 to initiate the second transition which terminates the pulse.

The diodes 29 and 50 make the time constant of the loop around capacitor 28 much longer for positive alternations of the squarewave 51 than for the negative alternations. This permits negative spikes of short duration and large amplitude to be applied to the grid of tube 16 to initiate the pulses, while allowing the positive portions of the timing signal to be increased in duration and reduced in amplitude sufliciently as to be relatively ineffective to terminate the pulses.

What is claimed is:

1. In a system for injecting measured amounts of fuel into the cylinders of an internal combustion engine in synchronism with the rotation thereof in which there is provided an electrical circuit including a monostable multivibrator and means causing said multivibrator to produce a series of pulses of electrical current synchronized with the rotation of said engine and means responsive to each of said pulses to inject fuel into a cylinder of said engine for the duration thereof, means for controlling the duration of said pulses in response to the operation of the throttle of said engine comprising: means applying a bias voltage to said multivibrator to control the duration of said pulses, means responsive to the position of said throttle to fix the level of said bias voltage, and means responsive to movement of said throttle in a sense to increase the level of said bias voltage to temporarily raise said level above that corresponding to the instantaneous position of said throttle, the magnitude of said temporary rise being a function of the rate of movement of said throttle.

2. In a system for injecting measured amounts of fuel into the cylinders of an internal combustion engine in synchronism with the rotation thereof in which there is provided an electrical circuit including a multivibrator and means causing said multivibrator to produce a series of pulses of electrical current synchronized with the rotation of said engine and means responsive to each of said pulses to inject fuel into a cylinder of said engine for the duration thereof, means for controlling the duration of said pulses in response to the operation of the throttle of said engine comprising: means applying a bias voltage to said multivibrator to control the duration of said pulses, means responsive to the position of said throttle to fix the level of said bias voltage, and means responsive to movement of said throttle in a sense to increase the level of said bias voltage to temporarily raise said level above that corresponding to the instantaneous position of said throttle, the last named means including a resistive voltage divider shunted by a capacitive voltage divider, said capacitive voltage divider having an output of higher level than said resistive voltage divider, the difference between said levels being a function of the rate of movement of said throttle.

3. In a system for injecting measured amounts of fuel into the cylinders of an internal combustion engine in synchronism with the rotation thereof in which there is provided an electrical circuit including a monostable multivibrator and means causing said multivibrator to produce a series of pulses of electrical current synchronized With the rotation of said engine and means responsive to each of said pulses to inject fuel into a cylinder of said engine for the duration thereof, means for controlling the duration of said pulses in response to the operation of the throttle of said engine comprising: means applying a bias voltage to said multivibrator to control the duration of said pulses, means responsive to the position of said throttle to fix the level of said bias voltage, and means responsive to movement of said throttle in a sense to increase the level of said bias voltage to ternporarily raise said level above that corresponding to the instantaneous position of said throttle, the last named means comprising a pair of serially connected resistors connected to the input of said multivibrator in a manner to act as a resistive voltage divider for voltages applied thereto, and a capacitor shunting each of said resistors, the capacitances of said capacitors being such as to apply to said input a higher value of voltage than is applied by said resistive voltage divider, Whenthe voltage applied to said resistive voltage divider is increased, the difference between said values being a function of the rate of said increase.

No references cited. 

